A hemi-arthroplasty bone joint implant has a first part (120) with a stem (111) tor intramedullary implanting into a metacarpal, and a second part (110) to engage the trapezium is a translational manner, a hemi-arthroplasty articulating coupling (121). This allows multi-axial motion with translational movement of the second part over the trapezium and rotation of the first part (110) about the articulating coupling (121, 103). There is also a converter to convert the implant to a toral arthroplasty implant in situ during revision surgery. The second part (110) and the hemi-arthroplasty coupling (100, 123, 121) are removable in situ during revision surgery. The first part (120) has an engagement threaded socket (117) for, after removal of the second part and the hemi-arthroplasty coupling, engaging the replacement coupling (200) and allowing mutual articulation of the first (120) and replacement parts (220). This forms a total arthroplasty joint implant.

A prosthetic joint includes: (a) a first member comprising rigid material and having a perimeter flange defined by an undercut groove, the flange defining a wear-resistant first contact surface having a protruding rim; (b) a second member comprising rigid material and having a perimeter flange defined by an undercut groove, the flange defining a wear-resistant, second contact surface having a protruding rim; and (c) a third member comprising rigid material positioned between the first and second members, the third member defining opposed wear-resistant third and fourth contact surfaces; (d) wherein the first and second contact surfaces bear against the third and fourth contact surfaces, to transfer loads through the member, while allowing pivoting motion between the first and second members; (e) wherein the flanges can deform elastically such that the first and second contact surfaces conform to the third and fourth contact surfaces.

A prosthesis system comprises plates that can be positioned against vertebrae and a selected resilient core that can be positioned between the plates to allow the plates to articulate. The selected resilient core can be chosen from a plurality of cores in response to patient characteristics, such as age and/or intervertebral mobility, such that the prosthesis implanted in the patient is tailored to the needs of the patient. The plurality of cores may comprise cores with different resiliencies, and one of the cores can be selected such that the upper and lower plates articulate with the desired shock absorbing resiliency and/or maximum angle of inclination when the one selected core is positioned between the plates.

Superior and/or inferior facets of one or more facet joints may be replaced by superior and/or inferior facet joint prostheses. In one embodiment, a kit of superior or inferior prostheses is provided, in which the prostheses have at least two dimensions that vary among members of the kit independently of each other. Each prosthesis may have a bone engaging surface having a surface that is polyaxially rotatable against a corresponding resection of a vertebra. Each prosthesis may also have an articulating surface shaped such that, after attachment to the spine, the replaced or partially replaced facet joints provide a larger medial-lateral range of motion when the spine is flexed than when the spine is extended. Crosslinks may be used to connect left and right prosthesis together in such a manner that they are stabilized in a position in which they are seated directly against the vertebra.